It is known that a clathrate hydrate such as a TBAB hydrate to be generated by cooling a tetrabutylammonium bromide (TBAB) aqueous solution has a large heat density and is used as a cold storage material. In regard to such a clathrate hydrate, a single clathrate hydrate can be used as a heat storage material and multiple types of clathrate hydrates can be used as a heat storage material after being mixed with each other (see Patent Literature 1). However, the aqueous solution that generates a clathrate hydrate easily enters a supercooled state in which a hydrate is not generated even when the aqueous solution is cooled to a hydrate generation temperature or lower. Therefore, it is difficult to stably use the aqueous solution as a cold storage material.
Meanwhile, a technique of releasing the supercooled state by applying an electric field to a TBAB aqueous solution in the supercooled state has been reported (see Non Patent Literature 1). In this method, a mechanism in which a supercooling release material is generated in a portion of the TBAB aqueous solution to which the electric field is applied, generation of a crystal nucleus is supported by the supercooling release material to release the supercooled state, and then the supercooled state is gradually released from the portion for a crystal growth of a TBAB hydrate is assumed.
However, in the method described in Non Patent Literature 1, details of the supercooling release material to be generated in the case where the electric field is applied to the TBAB aqueous solution are unclear and reported cases having a description on what kind of a material the supercooled state of the TBAB aqueous solution is released by do not exist.